Use the tonic namespace for tonic + resulting build fixes

tonic/dart_wrappable.h

Index: tonic/dart_wrappable.h
diff --git a/tonic/dart_wrappable.h b/tonic/dart_wrappable.h
index 94286013bbcdab4e57e22f8ae57be22598b3cc7b..6bb4993379d326e915657205cb23a4d7491de1df 100644
--- a/tonic/dart_wrappable.h
+++ b/tonic/dart_wrappable.h
@@ -13,7 +13,7 @@
 #include "tonic/dart_state.h"
 #include "tonic/dart_wrapper_info.h"
 
-namespace blink {
+namespace tonic {
 class DartGCVisitor;
 struct DartWrapperInfo;
 
@@ -130,6 +130,6 @@ inline T* GetReceiver(Dart_NativeArguments args) {
   return static_cast<T*>(reinterpret_cast<DartWrappable*>(receiver));
 }
 
-}  // namespace blink
+}  // namespace tonic
 
 #endif  // SKY_ENGINE_TONIC_DART_WRAPPABLE_H_